In a number of industrial processes a relatively cool feed liquid is fed into a vessel and mixed with relatively hot liquid therein. Examples include heat exchangers and steam generators. For example, in a steam generator such as a boiling water nuclear reactor, the heat source is a nuclear fuel core contained in a pressure vessel. Arrangements for effecting the feeding and mixing are well known in the art.
One type of such arrangement includes an inlet conduit connected to the vessel by an inlet nozzle. A sparger disposed within the vessel has at least one outlet port adapted to introduce the feed liquid as a high-velocity jet into the body of liquid in the vessel. A sparger supply line is disposed within the nozzle and places the inlet conduit in flow communication with the sparger so that feed liquid is conducted from the inlet conduit to and through the outlet port. The outer surface of at least a portion of the supply line is spaced from the inner surface of the nozzle to define therebetween an annular cavity opening into the vessel. (Such sparger supply lines are sometimes referred to in the art as "thermal sleeves.") In the prior art arrangements various seals have been employed between an upstream portion of the supply line and the nozzle in attempting to provide arrangements wherein the relatively cool feed liquid is confined within the sparger supply line. Typically, however, such seals have been imperfect, whereby an amount of the feed liquid leaks past the seal. This leakage flow, which as indicated above is relatively cool, flows through the annular cavity adjacently along the inner surface of the nozzle and enters the vessel-contained liquid body adjacent the downstream end of the nozzle, e.g. at the nozzle blend radius. In such arrangements after varying periods of use, cracks have been discovered along the inner surface and blend radius of the inlet nozzle. These cracks are believed to result from thermal cycling of the inner portion of the nozzle by alternate exposure to the hot water or other liquid in the vessel and to the relatively cooler feed water or water cooled by the feed water.
An improvement of the above-described arrangement is described by Sheer, Jr. in U.S. patent application Ser. No. 927,384, filed July 24, 1978, assigned to the assignee hereof and incorporated herein by reference. That improvement includes an ejector thermal sleeve having an upstream portion disposed within the annular cavity. The upstream portion circumferentially surrounds, and is spaced from, a downstream portion of the sparger supply line. The upstream sleeve portion is sealed to the inlet nozzle to substantially preclude leakage flow into the vessel along the downstream end of the nozzle. A downstream portion of the ejector thermal sleeve in flow communication with the upstream portion thereof circumferentially surrounds, and is spaced from, the sparger outlet port in liquid-ejecting register therewith to define an ejector chamber opening into the vessel. In operation, feed liquid leakage flow is confined to the interior of the ejector thermal sleeve and ejected from the chamber by and with the feed liquid flow exiting through the outlet port.
Although the improved arrangement of Sheer, Jr. is a substantial advance in the art, further improvements are desirable for further reducing the foregoing cracking problem.
This problem is discussed in greater detail in copending application of Jacobson et al., U.S. Ser. No. 887,471, filed Mar. 17, 1978, now U.S. Pat. No. 4,168,071 assigned to the assignee hereof and incorporated herein by reference. That application describes a thermal isolator arrangement which offers one approach to substantially eliminating thermal cycling of the inner portion of the inlet nozzle and resulting thermal cracking thereof. The present invention is neither disclosed nor suggested by the referenced applications.
It has now been found, by practice of the present invention, that the improved arrangement described in the referenced Sheer, Jr. application can be further improved by elimination of the seal between the inlet nozzle and the ejector thermal sleeve without loss of control of the feed liquid leakage flow path. The ejective action of the main flow of the feed liquid exiting through the outlet port additionally draws an insulating flow of hot liquid from the pressure vessel sequentially upstream through a radially outer portion of the annular cavity (i.e. the portion lying radially outwardly of the ejector thermal sleeve and radially inwardly of the nozzle), into the interior of the upstream portion of the sleeve and downstream with the leakage flow therethrough, the liquid drawn from the vessel being returned thereto through the ejector chamber.